Self-compensating amplifier tube circuit



April 24, 1945. P. GLASS 2,374,480

SELF-COMPENSATING AMPLIFIER TUBE CIRCUIT Filed Jan. 26, 1943 a C; I1 'j. 2

, vs l l6 SIGNAL souRcg soURcE AMPLIP.

sIGNHI. 21 souRcE 1 SUPILY PAUL elinss "cer Patent 2,124,882.

The advance of such a circuit is that it auto-- tube I input signals derived from a source S. is another coil of the magnetic system connected Patented Apr. 24, 19 45 I SELF-COMPENSATING AMPLIFIER TUBE Paul Glass, Chicago, Ili., ultim to Askania Regulator Company, a corporation of Illinois Application January 26. 1943, Serial No. 473,648

- This invention relates to'a novel self-compeneating amplifier circuit for use in A. C. or D. C.

translation or controlling devices. More particularly it relates to a magnetically controlled gas or vapor discharge tube. as for instance the tube which is known as the permatron. This type of tube is disclosed in Electrical Engineering, May. 1989, volume 58. pages .224 to 228; see also Spenmatically. compensates within the rangeof its characteristics for variations which are due to heater current variations, individual tube char,- aeteristics, and changes of tube performance which may be a function of time-'and'variables,

and which may sheet the output of the tube in relation to the input signal.

This arrangement, and particularly the use of a gaseous types f'tube in the circuit. has a great advantage in that it permits a control of considerable current with very small signals, or, in other words, great amplifications with definitely ad- .iustable amplification factors. 1

Further aims and advantages of the invention will appear in the specification when considered inmconnh ection with the accompanying drawing, in w c Figure 1 shows a self-compensating current amplifier with separate and independent feed back, em odying the features of my invention.

Figure 2 is a modified form of theinvention I shown in' Figure 1 with a series circuit feed back.

Figure 3 is a modified form of the invention shown in Figure 2 embodying a, signal preamplifier in-the circuit.

Figure 4 shows another modification of the form of the invention shown in Figure 1.

As is well known, a considerable amount of current fiows through a gaseous or vapor discharge tube or the permatron type. As soon asgthe mag- -neticfield produced by the signal reaches a dennite lilfiit value, the tube-then becomes conduc-,.

tive until such time as the tube current is interrupted by reversal of the alternating plate voltage or any other means of interrupting the circuit. In'l'ig. 1, i represents a tube of the permatron type with its filament'or'cathode 2, its anode. l, and its collector electrode la. 4 is the signal input coil arranged and disposed to impress on tlli:

to a source it of biasing voltage of suitable mag- .hltude andserving to deflect the electrons from "cathode 2 onto collector electrode to. l is. an

Claims. (Cl. 179-171) netic field produced by the signal in said first coil 4 and energized from the outputof the circuit, as will be described later.

The plate is connected through an ammeter 6 and a load (represented by resistance 1) to one terminal of an alternating voltage supply II of suitable and preferably high frequency, while the other terminal of said voltage source 2| is connected to the cathode 2. The voltage across the load resistor I is applied to a potentiometer Ii and an adjustable part of this voltage is applied .to. a condenser-resistance-network 9-40. The

terminals of the condenser U are connected to the additional controlcoil I. The polarity of the connections is such that the magnetic field produced by I is opposed to the field or coil 4 which isthe result of the signal. A voltage meter II is connected across condenser I.

Assuming that a signal, for instance a D. C. voltage, is applied to the controlling coil 4, the

. tube will fire during positive half cycles of the supply voltage and current will fiow in the plate circuit, it being understood that in the absence of a signal the biasing field prevents the tube from The result of this output or plate 4 current will be a voltage drop across the load i which charges the condenser 8 through variable resistor .II to a value which is determined by the adjustment or the potentiometer I. The condenser discharges relatively slowly through control coll I and thereby produces a magnetic field counteracting or nullifying the eifect of the magnetic field produced by the signal coil 4. As soon I as the counteracting force produced by coil 6 is equal to that of the signal produced by coil 4, the

tube fails to fire at the beginning of .a positive half cycle of the supply voltage. The number of firing cycles and their ratio to the number of nonconducting cycles is thus automatically con-' trolled by the circuit and a resultant average output current obtained which is directly proportional-to the np t signaL- By choice of a suitable frequency of the plate voltage supply and the time constant of the condenser-resistancecircuitF-l I, the variations of the condenser volt I age can be practically eliminated. By an adjust ment of the potentiometer I, different amplifica-= tion ratios between input and output can be oblfn Fig. 2 a modification oithe above circuit is shown, identical numbers designating identical parts. It will be noted that the condenser-resistance-network l-ll is connected in series with additional coil arranged to counteract the ma and in opposition to the input signal source S and not separated as in Fig. l. The Joint effect of the condenser-resistance-networl 9II and the signal source are in this form applied to a coil 20 which serves the combined functions of the coils 4 and 5 in the form oi-the invention shown in Fig. 1.

In Fig. 3 an arrangement is shown which is suitable for relatively great amplifications of signal voltages, again identical numbers designating parts which were described in connection with Fig. 1. The difference as compared with Fig. 1'

is that the signal voltagev is applied to an amplifier l2 which produces the controlling current and a condenser connected in series across the applied to the coil 8. The feed back circuit is similar to the one described in connection with Fig. 2 and is in series connection with and opposed to the signal source S. A separate coil 18 and voltage source it is provided for a suitable bias or the tube.

' In Fig. 4 the circuit of Fig. 1 is modified by providing a filter circuit 69, as known in the art, in the output circuit of the tube, in order to smoothen out. any variations of the output voltage which may appear across condenser 9. In this form of the invention, provision is made whereby the coils and it of Fig. 1 may be replaced by a single coil 22. To that end, the

coil 22 is connected in series with potentiometers' to the particular circuits as shown and described,

but said circuits are capable of various modifications. .1

I claim as my invention 1. An amplifier circuit comprising, in combination, a magnetically controlled gaseous discharge tube, a plate circuit for said tube including a load and an' alternating current voltage source, means for impressing on said tube a signal to be amplified, means for placing a bias on said tube, and a circuit deriving its energy from said tube arranged-to counteract the effect of a signal acting on said tube through said first adjustable portion ot said last mentioned means, said condenser being also connected in the circuit for said coilfin series opposition to said signal source.

5, An amplifier circuit. comprising, in combination, a "magnetically controlled discharge tube, a plate circuit for said tube including a load and an alternating current voltage source, means for biasin said tube, a coil disposed to have its magnetic field impressed on said tube to exercise control thereover', means connected to said 'plate circuit to obtain an adjustable voltage, a resistance and a condenser connected I energizing circuit for said coil including in series mentioned means in such manner as to produce -an output current substantially proportional to and means connected across said condenser and arranged to counteract the efiect of a signal acting on said tube through said first mentioned the variable portions of a first and a second potentiometer, said first '1 potentiometer being and means for connecting said second coil to receive its energization from said condenser and disposed to counteract the efiect of the field pro- I duced by said first coil when a signal is supplied thereto.

7. An amplifier circuit comprising, in combination, a magnetically controlled gaseous discharge tube, a plate circuit for said tube inmeans in such manner as to produce an output current substantially proportional to the input nected to said platecircuit to obtain an adjust-- able voltage, a resistance and a condenser con-.

nectedin series across the adjustable portion of said last mentioned means, and a second coil connected across said condenser and disposed to impress its field upon said tube in a manner to eluding a series impedance element and a source of alternating current voitagefimeans for applying to said tube a biasing magnetic field to prevent firing of said tube in the absence of a signal, means controlled by input signals to cause firing of said tube, a condenser connected to be charged by the voltage drop across said impedance element. and a magnetizing coil 7 energized from said condenser for acting on said tube in opposition to said input signals.

8. An amplifier circuit according to claim 7 wherein a resistance element is included in the charging circuit of said condenser.

9. An amplifier circuit according to claim 7 wherein a resistance element is included in the 10. An amplifier circuit comprising, in comto be charged by the voltage drop across said bination, a magnetically controlled discharge impedance element, and magnetic means enertube, a plate circuit for said tube including a giined from said condenser and acting on said series impedance element and a, source of altertube to vary the plate current in opposition to nating current voltage, magnetic means con- 5 said input signal. trolled by input signals to vary the flow of cur- Y PAUL GLASS. rent in said plate circuit, a condenser connected 

